Add audio player

Play the decoded audio using SDL.

The audio player frame sink receives the audio frames, resample them
and write them to a byte buffer (introduced by this commit).

On SDL audio callback (from an internal SDL thread), copy samples from
this byte buffer to the SDL audio buffer.

The byte buffer is protected by the SDL_AudioDeviceLock(), but it has
been designed so that the producer and the consumer may write and read
in parallel, provided that they don't access the same slices of the
ring-buffer buffer.

PR #3757 <Genymobile/scrcpy#3757>

Co-authored-by: Simon Chan <1330321+yume-chan@users.noreply.github.com>

Author: rom1v

BUILD.md

@@ -15,7 +15,7 @@ First, you need to install the required packages:
 sudo apt install ffmpeg libsdl2-2.0-0 adb wget \
                  gcc git pkg-config meson ninja-build libsdl2-dev \
                  libavcodec-dev libavdevice-dev libavformat-dev libavutil-dev \
-                 libusb-1.0-0 libusb-1.0-0-dev
+                 libswresample-dev libusb-1.0-0 libusb-1.0-0-dev
 ```
 
 Then clone the repo and execute the installation script
@@ -94,7 +94,7 @@ sudo apt install ffmpeg libsdl2-2.0-0 adb libusb-1.0-0
 # client build dependencies
 sudo apt install gcc git pkg-config meson ninja-build libsdl2-dev \
                  libavcodec-dev libavdevice-dev libavformat-dev libavutil-dev \
-                 libusb-1.0-0-dev
+                 libswresample-dev libusb-1.0-0-dev
 
 # server build dependencies
 sudo apt install openjdk-11-jdk

app/meson.build

@@ -4,6 +4,7 @@ src = [
     'src/adb/adb_device.c',
     'src/adb/adb_parser.c',
     'src/adb/adb_tunnel.c',
+    'src/audio_player.c',
     'src/cli.c',
     'src/clock.c',
     'src/compat.c',
@@ -30,6 +31,7 @@ src = [
     'src/version.c',
     'src/video_buffer.c',
     'src/util/acksync.c',
+    'src/util/average.c',
     'src/util/bytebuf.c',
     'src/util/file.c',
     'src/util/intmap.c',
@@ -100,6 +102,7 @@ if not crossbuild_windows
         dependency('libavformat', version: '>= 57.33'),
         dependency('libavcodec', version: '>= 57.37'),
         dependency('libavutil'),
+        dependency('libswresample'),
         dependency('sdl2', version: '>= 2.0.5'),
     ]
 
@@ -135,6 +138,7 @@ else
             cc.find_library('avcodec-60', dirs: ffmpeg_bin_dir),
             cc.find_library('avformat-60', dirs: ffmpeg_bin_dir),
             cc.find_library('avutil-58', dirs: ffmpeg_bin_dir),
+            cc.find_library('swresample-4', dirs: ffmpeg_bin_dir),
         ],
         include_directories: include_directories(ffmpeg_include_dir)
     )